With the development of national economy， combustible gas has been widely used in production and life. But its flammable and explosive characteristics seriously threaten the safety of public property and life. This paper introduces the development process and characteristics of combustible gas sensor: catalytic combustion type has the characteristics of accurate measurement and fast response， while it doesn't have selectivity; semiconductor type has low price and wide popularity， but it is greatly affected by the environment， and it is not applicable to places with accurate measurement; electro-chemical type has strong selectivity， good temperature characteristic， but the service life of it is relatively short; infrared type has wide measurement range， high accuracy， but it is expensive. In detection of combustible gas， sensors will gradually achieve low power consumption， miniaturization， intelligence and integration， and it will make further breakthroughs in interdisciplinary horizontal fields. The sensor integrating management data， emergency initiative and intelligent equipment will be the key to build smart cities and smart parks.